#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint998244353;
//const int mod = 998244353;
//using mint = modint1000000007;
//const int mod = 1000000007;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	struct Edge {
		int to;
		int type;
	};
	dsu uf(n);
	vector<vector<Edge>>to(n);
	rep(i, m) {
		int a, b, c;
		string s;
		cin >> a >> s >> b;
		a--, b--;
		if ("<==>" == s) c = 0;//同色
		else c = 1;
		to[a].push_back({ b, c });
		to[b].push_back({ a, c });
		uf.merge(a, b);
	}
	vector<int>dp(n);
	auto dfs = [&](auto self, int v, int p = -1)->bool {
		if (0 == dp[v])dp[v] = 1;
		for (auto e : to[v]) {
			if (0 != dp[e.to]) {
				if (0 == e.type) {
					if (dp[e.to] != dp[v])return false;
				}
				else {
					if (dp[e.to] == dp[v])return false;
				}
			}
			else {
				if (0 == e.type) dp[e.to] = dp[v];
				else dp[e.to] = -dp[v];
				auto get = self(self, e.to, v);
				if (!get) return false;
			}
		}
		return true;
	};
	bool chk = true;
	rep(i, n) {
		if (0 != dp[i])continue;
		auto get = dfs(dfs, i);
		if (!get)chk = false;
	}
	if (!chk) {
		cout << "No" << endl;
		return 0;
	}
	auto g = uf.groups();
	vector<int>ans;
	rep(i, g.size()) {
		vector<int>v0, v1;
		for (auto e : g[i]) {
			if (-1 == dp[e])v0.push_back(e);
			else v1.push_back(e);
		}
		if (v0.size() < v1.size())swap(v0, v1);
		rep(i, v0.size())ans.push_back(v0[i]);
	}
	sort(all(ans));
	cout << "Yes" << endl;
	cout << ans.size() << endl;
	rep(i, ans.size())cout << ans[i] + 1 << " ";
	cout << endl;
	return 0;
}